Passive valve assembly for vehicle exhaust system

ABSTRACT

A passive valve assembly for a vehicle exhaust system includes an exhaust component that defines an exhaust gas flow path and a vane that is positioned within the exhaust gas flow path. The vane is movable between a fully closed position where a maximum portion of the exhaust gas flow path is blocked by the vane and a fully open position where a minimum portion of the exhaust gas flow path is blocked by the vane. The closed position comprises a start position for the passive valve assembly when there is no exhaust gas flow. The vane is obliquely orientated to a plane that is perpendicular to a centerline of the exhaust component when the vane is in the start position.

RELATED APPLICATIONS

This application claims priority to provisional application No. 60/989,508 filed on Nov. 21, 2007.

TECHNICAL FIELD

The subject invention relates to a passive valve assembly in a vehicle exhaust system, and more particularly to a passive valve assembly that has a non-vertical start position relative to exhaust gas flow to reduce valve flutter.

BACKGROUND OF THE INVENTION

Exhaust systems are widely known and used with combustion engines. Typically, an exhaust system includes exhaust tubes that convey hot exhaust gases from the engine to other exhaust system components, such as mufflers, resonators, etc. Mufflers and resonators include acoustic chambers that cancel out sound waves carried by the exhaust gases. Although effective, these components are often relatively large in size and provide limited nose attenuation.

Attempts have been made to improve low frequency noise attenuation by either increasing muffler volume or increasing backpressure. Increasing muffler volume is disadvantageous from a cost, material, and packaging space perspective. Increasing backpressure can adversely affect engine power.

Another solution for reducing low frequency noise is to use a passive valve assembly. Passive valve assemblies are either installed within a muffler, or are installed in a by-pass pipe configuration. Both of these known arrangements have certain disadvantages. Passive valves installed within mufflers are subjected to high temperatures, which limit the passive valve's effectiveness from material and cost perspectives. By-pass configurations are disadvantageous from material cost and packaging perspectives.

Also, the inclusion of the passive valve assembly within the exhaust system presents additional noise challenges, which must be addressed. The passive valve assembly includes a flapper valve body or vane that is positioned within an exhaust pipe, with the vane being pivotable between an open position and a closed position. In a fully open position exhaust gas flow is maximized, and in a fully closed position exhaust gas flow is minimized. The passive valve is spring biased toward the closed position, and when exhaust gas pressure is sufficient to overcome this spring bias, the vane is pivoted toward the open position. When the exhaust gas pressure falls below the biasing force, the spring causes the vane to return to the closed position.

Traditionally, when the vane is positioned such that the passive valve assembly is “closed” (also referred to as a starting position for the valve), the vane is orientated to be perpendicular to a direction of exhaust gas flow. In other words, a main body structure of the vane is positioned to be perpendicular to a pipe centerline of the exhaust pipe when the vane is at its starting position. The starting position corresponds to a no-flow, or a low flow, of exhaust gas through the exhaust pipe.

One disadvantage with this traditional orientation is that valve flutter is generated with pressure fluctuation as the vane starts to move from the closed position toward the open position. As such, these pressure fluctuations, i.e. small increases and decreases in gas flow pressures at lower engine operating speeds, can cause the vane to accordingly pivot back and forth (flutter) resulting in a generation of undesirable noise referred to as “chatter.”

Therefore, there is a need to provide a passive valve arrangement that can overcome the disadvantages of by-pass and internal muffler mount configurations while effectively and efficiently operating to attenuate low frequency noise and reduce valve flutter/chatter.

SUMMARY OF THE INVENTION

A passive valve assembly for a vehicle exhaust system includes a vane that is positioned within an exhaust gas flow path. The vane is orientated to be non-perpendicular to a direction of exhaust gas flow when in a start position.

In one example, the passive valve assembly includes an exhaust component that defines the exhaust gas flow path. The vane is movable between a fully closed position where a maximum portion of the exhaust gas flow path is blocked by the vane and a fully open position where a minimum portion of the exhaust gas flow path is blocked by the vane. The closed position comprises the start position for the passive valve assembly when there is no exhaust gas flow or minimal exhaust gas flow. The vane is obliquely orientated relative to a plane that is perpendicular to a centerline of the exhaust component when the vane is in the start position.

In one example, the vane is orientated at an angle relative to the plane where the angle is within a range of 10 to 35 degrees.

In one example, a stop is mounted within the exhaust gas flow path to engage a tip of the vane. The stop defines the start/closed position such that the vane can be repeatedly returned to a consistent start position.

This configuration provides a non-bypass exhaust gas flow path that is 80%-97% blocked when the vane is in the closed position in combination with providing a rapid open area change with only a small angle change at initial vane lift-off from the start/stop position. These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of one example of an exhaust component and passive valve assembly.

FIG. 2 shows a side view of an exhaust component with a stop for a vane.

FIG. 3 is a graph that shows blockage of an exhaust gas flow path vs. opening angle of the vane.

FIG. 4 is a schematic view of the exhaust component and passive valve assembly of FIG. 1 within an exhaust system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, an exhaust component, such as an exhaust tube or pipe 10 includes an exhaust throttling valve, referred to as a passive valve assembly 12. The passive valve assembly 12 is movable between an open position where there is minimal blockage of an exhaust gas flow path 16 and a closed position where a substantial portion of the exhaust gas flow path 16 is blocked. The passive valve assembly 12 is resiliently biased toward the closed position and is moved toward the open position when exhaust gas flow generates a pressure sufficient enough to overcome the biasing force.

In the example shown, the exhaust pipe 10 comprises a single pipe body 14 that defines the exhaust gas flow path 16. In one example, the pipe body 14 includes a curved outer surface 14 a and a curved inner surface 14 b that defines the exhaust gas flow path 16. In one example, the pipe body 14 has a circular cross-section.

The passive valve assembly 12 includes a valve body or vane 18 that blocks a portion of the exhaust gas flow path 16 when in the closed position. As discussed above, the vane 18 is pivoted toward the open position to minimize blockage of the exhaust gas flow path 16 in response to pressure exerted against the vane 18 by exhaust gases.

In one example, the vane 18 is fixed to a shaft 20 with a connecting arm, shown schematically at 22 in FIG. 1. A slot 24 is formed within the curved outer surface 14 a of the pipe body 14. A housing 26, shown in this example as a square metal structure, is received within this slot 24 and is welded to the pipe body 14. Other housing configurations could also be used. The shaft 20 is rotatably supported within the housing 26 by first 28 and second 30 bushings or bearings and defines an axis of rotation A.

The first bushing 28 is positioned generally at a first shaft end 32. The first bushing 28 comprises a sealed interface for the first shaft end 32. The shaft 20 includes a shaft body 34 that has a first collar 36 and a second collar 38. The first bushing 28 includes a first bore that receives the first shaft end 32 such that the first collar 36 abuts directly against an end face of the first bushing 28 to provide a sealed interface. As such, exhaust gases cannot leak out of the first bushing 28 along a path between the shaft 20 and first bushing 28.

The second bushing 30 includes a second bore through which the shaft body 34 extends to a second shaft end 40. The second collar 38 is located axially inboard of the second bushing 30. The shaft 20 extends through the second bore to an axially outboard position relative to the second bushing 30. A resilient member, such as a spring 42 for example, is coupled to the second shaft end 40 with a spring retainer 44. The spring retainer 44 includes a first retainer piece 46 that is fixed to the housing 26 and a second retainer piece 48 that is fixed to the second shaft end 40. One spring end 50 is associated with housing 26 via the first retainer piece 46 and a second spring end (not viewable in FIG. 1 due to the spring retainer 44) is associated with the shaft 20 via the second retainer piece 48.

The vane 18 comprises a body structure 60, such as a disc-shaped body for example, which includes a first portion 62 that is coupled to the shaft 20 with the connecting arm 22. The body structure 60 extends from the first portion 62 to a second portion that comprises a distal tip 64. As such, the tip 64 comprises a portion of the body structure 60 that is furthest from the axis of rotation A.

A stop 66 is supported by the pipe body 14 and is positioned within the exhaust gas flow path 16. The stop 66 defines the starting/closed position for the vane 18. The tip 64 of the vane 18 engages the stop 66 when the spring 42 returns the vane 18 from the open position to the closed position.

In one example, as shown in FIGS. 1 and 2, the stop 66 comprises a ramped surface 68 that begins at the inner surface 14 b at a position upstream from the vane 18 and extends outwardly away from the inner surface 14 b and towards the vane 18. The ramped surface 68 then transitions into a stopper end surface 70 that extends back towards the inner surface 14 b. The tip 64 of the vane 18 engages the stopper end surface 70 when in the closed position. This also defines the starting position for the vane 18 when there is no exhaust gas flow, or only a minimal amount of exhaust gas flow.

As shown in FIG. 2, the ramped surface 68 and the stopper end surface 70 are angled relative to the inner surface 14 b of the pipe body 14. The pipe body 14 defines a pipe centerline C, which is shown in FIG. 2. The ramped surface 68 is positioned at a ramp angle that is within a range of 10 to 45 degrees relative to the pipe centerline C. Similarly, the stopper end surface 70 is positioned at an angle relative to the pipe centerline C to define the start position. This will be discussed in greater detail below. In one example, the ramped surface 68 and the stopper end surface 70 are obliquely orientated relative to the inner surface 14 b and relative to the pipe centerline C.

In one example, a pad 72 is supported on the stopper end surface 70 to provide a cushioned surface to engage the tip 64 of the vane 18. The pad 72 can be made from a mesh material or other similar material, for example, and can be attached to the stopper end surface 70 with any type of attachment method suitable for use within an exhaust component.

The stop 66 is positioned at the tip 64 of the vane 18 to minimize closing forces. By positioning these contact surfaces as far as possible from the axis of rotation A, contact forces are reduced, which in turn increases durability. Further, the upstream ramped surface 68 of the stop 66 reduces backpressure, turbulence, and the generation of additional flow noise.

The vane 18 is positioned to provide an exhaust gas flow path that is 80%-97% blocked when the vane 18 is in the start/closed position, as well as being positioned to provide a rapid open area change with only a small angle change at initial vane lift-off from the start/stop position. The vane 18 is movable between a fully closed position where a maximum portion of the exhaust gas flow path 16 is blocked by the vane 18 and a fully open position where a minimum portion of the exhaust gas flow path 16 is blocked by the vane 18. As discussed above, the closed position also corresponds to the start position for the passive valve assembly when there is no, or low, exhaust gas flow. In this start position, the vane 18 is orientated to be non-perpendicular to a direction of the exhaust gas flow, which is indicated at 80 in FIG. 2.

As discussed above, the pipe body 14 defines a pipe centerline C that extends along a length of the exhaust pipe 10. The vane 18 is obliquely orientated relative to a plane P that is perpendicular to the pipe centerline C at the valve position in the exhaust gas flow path 16. As shown in FIG. 2, the vane 18 is orientated at an angle {acute over (α)} relative to the plane P that is within a range of 10 to 35 degrees. This angle {acute over (α)} is defined by the angle of the stopper end surface 70.

As shown in FIG. 3, orientating the vane 18 in such a manner provides significant operational advantages in additional to improving noise reduction. Small opening angle changes provide rapid increases in open area, i.e. blockage of the exhaust gas flow path 16 quickly decreases with only very small changes in the opening angle. This significantly reduces flutter behavior, which has been associated with a rate of change of open area from a start position.

In one example, shown in FIG. 4, the passive valve assembly 12 is positioned within an exhaust component 82. In this example, the exhaust component 82 comprises a pipe that has a first end 84 coupled to a first exhaust component 86 and a second end 88 coupled to a second exhaust component 90. The pipe comprises a non-bypass configuration with the pipe defining a sole exhaust gas flow path 92 between the first 86 and the second 90 exhaust components. A direction of exhaust gas flow is indicated by arrows 94. As such, the passive valve assembly 12 comprises the only valve assembly that is positioned in the gas flow path 92 between the first 86 and second 90 exhaust components.

In this configuration, as discussed above, the vane 18 is only pivoted from the start/closed position towards the open position in response to an exhaust gas flow 94 that exceeds a biasing force of the resilient member. As shown, the stop 66 is positioned to hold the vane 18 at the oblique starting angle. The resilient member returns the vane 18 into abutting engagement with the stop 66 when the exhaust gas flow is less than the biasing force of the resilient member.

The subject passive valve assembly 12 is configured to provide optimal function and durability. The vane 18, in its start/closed position, is positioned to be an angle {acute over (α)} between 10 and 35 degrees from the plane P perpendicular to the pipe centerline C at the valve position. This allows maximum closed position pressure drop with minimum angle to help stability against flutter/chatter. Further, this allows a range of coverage of 97%-80% to be attained in the closed position while also enabling rapid open area change with a small angle change at initial vane lift-off from start/stop.

Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention. 

1. A passive valve assembly for a vehicle exhaust system comprising: an exhaust component defining an exhaust gas flow path; and a vane positioned within the exhaust gas flow path, said vane having a fully closed position where a maximum portion of the exhaust gas flow path is blocked by said vane and a fully open position where a minimum portion of the exhaust gas flow path is blocked by said vane, said closed position comprising a start position for the passive valve assembly, and wherein said vane is orientated to be non-perpendicular to a direction of the exhaust gas flow when in said start position.
 2. The passive valve assembly according to claim 1 wherein said vane is orientated to be at an angle relative to the direction of the exhaust gas flow that is within a range of 10 to 35 degrees.
 3. The passive valve assembly according to claim 1 wherein said vane is positioned within said exhaust component in a non-bypass arrangement, and wherein said exhaust gas flow path is 80%-97% blocked when said vane is in said closed position.
 4. The passive valve assembly according to claim 1 wherein said exhaust component comprises an exhaust pipe defining a pipe centerline extending along a length of said exhaust pipe, and wherein said vane is obliquely orientated relative to a plane perpendicular to said pipe centerline.
 5. The passive valve assembly according to claim 4 wherein said vane is orientated at an angle relative to said plane that is within a range of 10 to 35 degrees.
 6. The passive valve assembly according to claim 1 wherein said passive valve assembly comprises the only valve assembly positioned within said exhaust component.
 7. The passive valve assembly according to claim 6 wherein said exhaust component comprises a non-bypass pipe with a first end to be connected to a first exhaust component and a second end to be connected to a second exhaust component and wherein said non-bypass pipe comprises the sole exhaust gas flow path between the first and the second exhaust components.
 8. The passive valve assembly according to 1 including a resilient member that biases said vane toward said closed position, said vane only being pivoted from said closed position towards said open position in response to an exhaust gas flow that exceeds a biasing force of said resilient member.
 9. The passive valve assembly according to claim 8 including a stop supported by said exhaust component and positioned within said exhaust gas flow path to engage a tip of said vane, said stop being positioned to hold said vane at an oblique angle relative to a plane that is perpendicular to a centerline of the exhaust component.
 10. The passive valve assembly according to claim 9 wherein said resilient member returns said vane into abutting engagement with said stop when the exhaust gas flow is less than said biasing force of said resilient member.
 11. The passive valve assembly according to claim 9 wherein said oblique angle is within a range of 10 to 35 degrees.
 12. A passive valve assembly for a vehicle exhaust system comprising: an exhaust pipe having an external surface and an internal surface that defines an exhaust gas flow path, said exhaust pipe having a first end to be connected to a first exhaust component and a second end to be connected to a second exhaust component such that said exhaust pipe provides a non-bypass pipe configuration between the first and the second exhaust components; a housing attached to said external surface; a shaft supported within said housing by at least one bushing, said shaft defining an axis of rotation; a vane positioned within the exhaust gas flow path, said vane having a fully closed position where a maximum portion of the exhaust gas flow path is blocked by said vane and a fully open position where a minimum portion of the exhaust gas flow path is blocked by said vane, said closed position comprising a start position for the passive valve assembly, and wherein said vane is obliquely orientated relative to a plane that is perpendicular to a pipe centerline of said exhaust pipe at a valve mount position when said vane is in said start position; and a resilient member that biases said vane toward said closed position, said vane only being pivoted from said closed position towards said open position in response to an exhaust gas flow that exceeds a biasing force of said resilient member.
 13. The passive valve assembly according to claim 12 including a stop positioned within said exhaust gas flow path to define said start position for said vane, and wherein a tip of said vane contacts said stop when said vane is pivoted to said closed position.
 14. The passive valve assembly according to claim 12 wherein said vane is orientated at an angle relative to said plane that is within a range of 10 to 35 degrees. 